It is known that electromagnetic pumps are employed for adding liquids, such as detergents, sanitisers, and disinfectants, to aqueous solutions through a predeterminable dosage repeatable in time.
In particular, the liquid is dosed into the solution through the mechanical action of an interposition membrane, moved by the action of two opposed forces: a pushing force, obtained through the magnetic attraction exerted on a ferromagnetic piston by an electromagnet, suitably driven by an electronic control circuit; and a return force, obtained through the repulsive action of a spring coaxial with the piston that is loaded by the same piston during the pushing phase.
However, presently available control circuits present some drawbacks.
In fact, traditional circuits supplying the electromagnet directly from the energy source, not taking the wide input voltage range into account, introduce large efficiency losses causing: scaling up to larger size the electromagnet; higher power consumption; an increase of temperature due to Joule effect of the electromagnet, limiting the so-called “time to fault” of the electromagnet and adjacent electronic components; and, consequently, an increase of manufacturing and maintenance costs.
In order to obviate such drawbacks, some solutions comprise some supplying circuits, interposed between the energy source and the electromagnet, for regulating the input voltage.
However, such traditional solutions also suffer from drawbacks.
First of all, even these driving circuits have high manufacturing and maintenance costs.
Moreover, traditional driving circuits do not allow an accurate regulation of the excitation current, that is substantially equal to a reference value valid in steady state, i.e. with warm electromagnet having a high resistive value of the winding, which value is at the beginning of operation, i.e. with cold electromagnet having a low resistive value of the winding, a value larger than necessary. This causes efficiency losses and a consequent higher power consumption, also making the electromagnet subject to rapid temperature increases due to Joule effect, limiting the “time to fault” of the electromagnet.
Finally, traditional driving circuits do not allow a precise detection of the position of the piston within the electromagnet, of which only completely outward or completely inward limit positions are substantially assumed.